The present application is related to the following three patent applications, all of which are specifically incorporated herein by reference, and all of which are being filed concurrently with the present application on the same date: Ser. No. 09/753,195, entitled xe2x80x9cSELF-VENTING CAP FOR A NECK OF A DEWAR VESSEL,xe2x80x9d Ser. No. 09/753,208, entitled xe2x80x9cSPECIMEN CHAMBER FOR A CRYOGENIC SHIPPING CONTAINER,xe2x80x9d and Ser. No. 09/753,207, entitled xe2x80x9cCONTAINMENT SYSTEM FOR SAMPLES OF DANGEROUS GOODS STORED AT CRYOGENIC TEMPERATURES.xe2x80x9d
The present invention is in the field of cryogenic shipping containers.
To ensure reproducible results in research and biotechnical processes, today""s scientists and clinical practitioners have found it necessary to genetically stabilize living cells and preserve the integrity of complex molecules for storage and transport. This is accomplished by containing these materials in enclosures where cryogenic temperatures are continuously maintained at or near liquid nitrogen or vapor phase liquid nitrogen temperatures (77K and 100K, respectively).
Advances in cryopreservation technology have led to methods that allow low-temperature maintenance of a variety of cell types and molecules. Techniques are available for the cryopreservation of cultures of viruses and bacteria, isolated tissue cells in tissue culture, small multi-cellular organisms, enzymes, human and animal DNA, pharmaceuticals including vaccines, diagnostic chemical substrates, and more complex organisms such as embryos, unfertilized oocytes, and spermatozoa. These biological products must be transported or shipped in a frozen state at cryogenic temperatures to maintain viability. This requires a shipping enclosure that can maintain a cryogenic environment for up to 10 days and meet other shipping requirements such as being relatively impervious to mechanical shock and effects of directional orientation.
In addition to the already existing difficulties posed in shipping heat-sensitive biologicals, the International Air Transport Association (IATA) imposed new regulations which became effective in January 1995 pertaining to all shipments that include specimens containing infectious agents or potentially infectious agents. These regulations, endorsed by the US Department of Transportation (DOT) and applicable to all public and private air, sea, and ground carriers, imposed greatly increased requirements upon shipping units to survive extensive physical damage (drop-testing, impalement tests, pressure containment tests, vibration tests, thermal shock, and water damage) without leakage and without fracture of the internal, primary receptacles (vials). Implementation of this regulation further complicated the shipping of frozen biologicals.
Even though bioshippers are currently available using liquid nitrogen as a refrigerant, little innovation has taken place in the design of packaging for low-temperature transport. Current shippers are generally vulnerable to the physical damage and changes in orientation encountered during routine shipping procedures. Additionally, these shippers rarely comply with the IATA Dangerous Goods Regulation (effective January 1995 or as later amended). Commercial vendors have not developed or certified a cost-effective, standardized shipping unit with the necessary specimen capacity and hold time to meet user demands.
One of the main criticisms of current shippers is price, which varies from $500.00 to $1,000.00 or more per unit. This substantially limits their use for the transport of many biologicals. Because of the initial cost and limited production of these containers, they are designed to be reusable. However, the cost of return shipping of these heavy containers is significant, particularly in international markets.
Users also complain about the absorbent filler used in the current dry shippers, which breaks down with continuous use, contaminating the interior of the container. In fact, one large user of these containers has essentially centered their entire shipping operation around cleaning the broken down absorbent material from the inside of these containers after each use.
Another problem cited by users of currently available dry shippers relates to the functional hold time versus static hold time. Static hold time pertains to a fully charged shipper with no heat load, sitting upright, e.g., essentially not in use. Functional hold time refers to the fully charged shipper in use and containing samples, e.g., in the process of being handled and transported. Even though the static hold time is often promoted as being 20 days, if the container is tilted or positioned on its side, the hold time diminishes to hours as opposed to days. This occurs because the liquid nitrogen transitions to the gaseous (vapor) phase more rapidly resulting in outgassing. The liquid nitrogen can also simply leak out of the container when it is positioned on its side.
The current cryogenic containers are promoted as being durable because they are of metal construction. However, rugged handling frequently results in the puncturing of the outer shell or cracking at the neck, resulting in loss of the high vacuum insulation. This renders them useless. The metal construction also adds to the weight of the container, thereby adding substantially to shipping costs.
Thus, there is a need for an improved cryogenic container that can be used to ship biologicals safely, reliably, and economically.
U.S. Pat. No. 6,119,465 seeks to meet this need by using unique, lightweight, low-cost, durable composites and polymers in a semi-disposable vapor phase liquid nitrogen bioshipper. This is accomplished in an inherently simple, reliable, and inexpensive device that will result in reduced shipping costs, enhanced reliability and safety, and fewer service requirements.
The present invention builds upon the framework laid by U.S. Pat. No. 6,119,465, the disclosure of which is specifically incorporated herein by reference. This is done by use of a cryogenic shipping container that has many significant advances over what is disclosed in our earlier patent. The end result is a much improved cryogenic shipping container that is more economical while still being reliable.
The present invention is generally directed to a portable, insulated shipping container. The shipping container has an outer shipping container shell and a support assembly for holding a dewar vessel within the outer shipping container shell and providing impact and vibration resistance to the dewar vessel. The dewar vessel has an inner vessel that holds a specimen chamber and plastic foam between its inner wall and the specimen chamber. The specimen chamber allows liquid cryogen to pass through it into the plastic foam, allows liquid cryogen in a vapor phase liquid state to pass from the plastic foam into it, and acts as a filter to prevent particles or fragments of the plastic foam from entering into it. It is preferred that the specimen chamber is an open-celled porous thermoplastic material that is cryogenically compatible, and it is especially preferred that it be an aerated polypropylene foam. It is preferred that the plastic foam is an open cell plastic foam, and it is especially preferred that it be a phenolic foam.
In a first, separate group of aspects of the present invention, the plastic foam can hold a normal charge of liquid cryogen in a dry vapor state regardless of the container""s spatial orientation. The plastic foam can be made of multiple foam segments having a maximum thickness less than a critical height with each segment being separated by a capillarity separation layer. The thickness of the foam segments is preferably selected so that the head pressure of the plurality of foam segments will not cause liquid cryogen to ooze or flow out of the foam segments when their spatial orientation is changed. This thickness can be less than approximately four inches. The foam can occupy substantially all of the volume between the inner wall of the inner vessel and the sample chamber. Materials suitable for use as the capillarity separation layer include paper products treated to resist water and spunbonded olefin film.
In other, separate aspects of the present invention, a self-venting cap is used to restrict access to the specimen chamber when it forms a compression seal with an inner circumference of the neck of the dewar vessel. The cap creates one or more tortuous paths through it when it is in the compression seal position. The cap can be made of a lower component with a first plurality of apertures, an upper component having a second plurality of apertures, a seal held between the lower and upper components, and a third component secured to the upper component. It is especially desirable that the components of the cap in the vapor paths are made of a cryogenically compatible material that is non-metallic and non-conductive. A first chamber can be formed between the lower and upper components while a second chamber and a vent opening can be formed between the upper and third components. Vapor can travel through the cap in any of multiple tortuous vapor paths beginning with the first plurality of apertures and then proceeding through the first chamber, the second plurality of apertures, the second chamber and then out a vent opening. One or more semi-permeable membranes can be used to prevent moisture (water vapor) from entering into the dewar vessel while still allowing vaporous cryogen to exit from the dewar vessel.
In still other, separate aspects of the present invention, the shipping container is configured so that a reservoir will be formed within the dewar vessel when the container rests on its side so that gravity will not force vapor phase liquid cryogen in the reservoir out of the dewar vessel. The reservoir can be formed by configuring the container so that there will be an angle of approximately six degrees or greater between a flat planar surface and a cross section of the specimen chamber taken from an upper end closest to its top wall and extending down through a lower end closest to its base when the side wall of the container is resting on the flat planar surface. The reservoir can also be formed by a plane that is substantially parallel to the flat planar surface which intersects with the base of the specimen chamber and a first aperture of a self-venting cap that forms a compression seal with the neck of the dewar vessel.
In yet still other, separate aspects of the present invention, the shipping container can have a funnel-shaped vessel plate affixed to the dewar vessel. The shipping container can be made of a rigid thermoplastic material having a base, a side wall and a top wall. The top wall can be connected to the side wall by a movable access assembly, such as a hinge and latching mechanism, and the latching mechanism can be held in a locked position by a lock. The side wall can include a top side wall with a pocket for holding paperwork and a top opening for accessing a dewar opening in the dewar vessel and the top side wall can be covered by the top wall. A safety strap with a locking mechanism, such as an adjustable buckle, can be affixed to the bottom of the dewar vessel and surround the dewar vessel in a closed position so that it also holds the self-venting cap in place. An inner plug of a cryogenically compatible insulating plastic foam with a handle can be held in the neck portion between the self-venting cap and the specimen container. The support assembly can have multiple parts or be a single piece, such as a material that is injected or poured into the shipping container""s shell to fill the available space.
In a further, separate aspect of the present invention, the portable shipping container can be made to comply with Department of Transportation/International Air Transport Association (DOT/IATA) Dangerous Goods Regulations.
Accordingly, it is a primary object of the present invention to provide an improved, portable, insulated shipping container that uses a dewar vessel that can be charged with a liquid cryogen.
This and further objects and advantages will be apparent to those skilled in the art in connection with the drawings and the detailed description of the preferred embodiment set forth below.